Question

ad-lib
 /ˈædˈlıb/  verb  , -libs, -libbed, -lib·bing
  : to make up words or music in a performance instead of saying or playing something that has been planned : improvise
   [  no obj  ] The actor forgot his lines, so he ad-libbed.
    a comedian who is admired for his ability to ad-lib
   [  + obj  ] The actor ad-libbed his lines.
    She ad-libbed the guitar solo.
    ad-lib a joke
  ad-lib  noun  ,  pl   -libs [  count  ]
   Some of the best jokes in the movie were ad-libs.
  ad-lib  adj  
   an ad-lib joke
  ad-lib  adv  
   did the whole dialogue ad-lib